Ankara — The incoming Biden administration's foreign policy priorities and worldview will collide with those of the Turkish government on several issues.

Why it matters: The U.S. needs its NATO ally Turkey for its efforts to contain Russia, counter Iran and deal with other crises in the Middle East. But relations between Biden and Turkish President Recep Tayyip Erdoğan are expected to be strained.

Erdoğan forged close personal ties with Trump, who prevented the implementation of sanctions against Turkey over business dealings with Iran and its purchase of a Russian S-400 missile defense system. (The S-400 purchase did lead the U.S. to expel Turkey from the F-35 program.)

• Trump also gave Erdoğan an almost free hand in his military operations in Syria.
• What to watch: After Trump leaves office, Ankara will no longer benefit from this shield. Potential sanctions under a less friendly White House would not only damage the economy, but also undermine the international prestige of a NATO ally.

Driving the news: Erdoğan was the last leader of a NATO ally to acknowledge Biden’s victory. Meanwhile, Turkey’s main secular opposition, the Republican People’s Party (CHP), and the pro-Kurdish People's Democratic Party (HDP) immediately congratulated him.

Flashback: Biden and Erdoğan have history. Back in 2014, a diplomatic crisis emerged between the two countries after Biden dropped a bombshell during an interview with the New York Times.

• Biden called Erdoğan an "autocrat" and said he would support the opposition's efforts to defeat him.
• Biden also implied that Turkey had helped the rise of ISIS by letting foreign fighters cross the border into Syria. He ultimately had to offer Erdoğan an official apology.

What they're saying: Biden’s 2014 remarks recently went viral in Turkey, leading Erdoğan to criticize him again.

• “Politicians in the U.S. don't even feel the need to hide their fascist plans about Turkey. They also don't hesitate to say in front of cameras that they want to achieve what they couldn't do with a coup by supporting the opposition," Erdoğan said after a Cabinet meeting. 

State of play: Erdoğan took several major domestic political steps in recent days, including replacing the central bank governor, which led to the resignation of the finance minister (who also happens to be his son-in-law).

• Later, Erdoğan announced an upcoming wave of democratic reforms, without revealing any details.
• He sent warm messages to both the EU and the U.S., saying that Turkey’s place is nowhere other than in Europe and that he wants to cooperate more closely with the U.S. 

What’s next: If Erdoğan wants to avoid a crisis with the Biden administration, he could freeze the S-400 deal with Russia, make symbolic democratic reforms or accommodate the Kurdish PYD forces in Syria.

• Such policies would require U-turns on a number of issues, but Erdoğan has proven to be pragmatic enough in the past.